1. Field of the Invention
The present invention relates to an apparatus for removing ash from repulped wastepaper. More particularly, the present invention relates to an apparatus for removing ash from repulped wastepaper which contains ash together with cellulosic fibers.
2. Information Disclosure Statement
Paper and paperboard products are typically manufactured from a pulp stock ejected from a headbox onto a fourdrinier forming wire. Such pulp stock is produced by various processes which include cooking wood chips in a caustic liquor. The aforementioned chips are provided by a chipper, fed with logs cut from trees.
Accordingly, the production of paper has required the planting of many millions of acres of trees which are grown and harvested in order to supply the necessary logs.
More recently, greater interest has been shown in recycling wastepaper. Such recycling helps in the conservation of natural resources. Accordingly, wastepaper has been collected and transported to pulping mills for treatment to provide pulp suitable for the production of paper.
However, repulping of wastepaper of necessity includes removal of printing ink and coloring matter. Various processes for removing ink are commercially available, including ink flotation cells and the like. Nevertheless, the removal of ash from the wastepaper has proved to be difficult and expensive.
More particularly, ash or clay is a powdered additive added to the pulp or paper web during formation thereof or more usually in a subsequent coating operation. The clay is added to the paper web in order to enhance the printability of the surface thereof. However, when such wastepaper is repulped, the clay or ash tends to be evenly distributed throughout the repulped stock. Such clay tends to inhibit the required hydrobonding or adhesion between adjacent fibers within the subsequently formed web.
Consequently, it is necessary to remove such ash from the repulped wastepaper before such repulped stock is ejected from a headbox to form a reprocessed web.
The present invention provides an apparatus for removing such ash from repulped wastepaper which contains the aforementioned ash together with cellulosic fibers.
Therefore, it is a primary object of the present invention to provide an apparatus which overcomes the aforementioned inadequacies of the prior art apparatus, and to provide an apparatus and method which makes a considerable contribution to the art of repulping wastepaper.
Another object of the present invention is the provision of an apparatus which includes a porous belt which moves between an upstream and a downstream roll for defining a screening portion such that repulped wastepaper is ejected from a headbox through the screening portion so that ash passes through the screening portion and cellulosic fibers are retained by the screening portion.
Another object of the present invention is the provision of an apparatus for removing ash from repulped wastepaper which includes drainage means disposed on the opposite side of a screening portion relative to a headbox for receiving ash passing through the screening portion.
Another object of the present invention is the provision of an apparatus for removing ash which includes a shower disposed adjacent to a cylindrical outer surface of a downstream roll for dislodging cellulosic fibers separated from the ash between a headbox and the downstream roll such that the fibers follow the cylindrical outer surface when a belt supported by the roll diverges relative to the outer surface.
Another object of the present invention is the provision of an apparatus for removing ash which includes a doctor disposed adjacent to the outer surface of a downstream roll for doctoring fibers from the outer surface.
Another object of the present invention is the provision of an apparatus for removing ash in which the repulped wastepaper is ejected at an angle within the range 40-20 degrees relative to a screen portion, so that fibers within the repulped wastepaper are prevented from flowing through the screening portion while ash and the like passes through the screening portion to a drainage means.
Another object of the present invention is the provision of a saveall pan which defines a weir, the weir being disposed between an upstream roll and a headbox such that ash separated from the repulped wastepaper flows in a direction from the headbox towards a downstream roll while water separated from the repulped wastepaper flows over the weir in a direction opposite to the direction of flow of the ash.
Other objects and advantages of the present invention will be apparent to those skilled in the art by consideration of the detailed description contained hereinafter, taken in conjunction with the annexed drawings.